mesa-users] Break-evens

Marcin @ astrophysics astrophysics at
Thu Dec 4 16:00:27 EST 2008

Hi Bill,

Bill Paxton wrote:
> One of the wonderful aspects of EZ was how fast it could do evolution 
> up the RGB.  EZ was based on Eggleton's code, and that was designed 
> specifically for thin shell burning up the RGB.  But I found that I 
> couldn't generalize it to let me do other stuff reliably.  So I've 
> abandoned the EZ methods.
Yes, now I can see it much closer. Anyway I still use EZ as an another 
approach to understand the stellar evolution.

> So mesa/star is slow up the RGB as it follows the shell burning in 
> detail.  However, I have been able to reach the helium core flash and 
> even continue through it to reach steady helium burning.   But it 
> currently requires some changes in parameter settings.  Since its been 
> some time since I've tried this, let me run some tests before I 
> suggest what you should do.
Calculations are slower but its very good to know that mesa does those 
details. It's another field for explorations. Let's just wait for your 
suggestions to parameter settings changes.

> So, mesa/star is sometimes (much) slower than EZ, but there are many 
> interesting things that mesa/star can do that I couldn't get EZ to do 
> at all.

>> And if we're talking about break-evens. What are the capabilities of 
>> mesa in this area?  Maybe it is possible to reach the point near to 
>> supernova expolsion?
> The eos at high T is based on Frank Timmes' code and should be fine 
> for advanced burning.
> The other parts of the mesa microphysics should also be capable of 
> supporting this.
> The problem at the moment is the breakdown of the convergence of the 
> structure equations.
> I'm currently working on a new approach to that problem, but it's too 
> early to tell if it will work.
I can't wait for it.

> (...) they should actually show helium shell flashes on the AGB.
I'll plot it out. I've already seen some mesa's loops on H-R diagram on 
Helium burning stage.

> The advanced burning stages after c12 are o16, ne20, mg24, si28, s32, 
> etc.  For carbon burning stars, I use
> new_net_num = 83 ! Basic + o18 + ne22 + alpha_mg24_to_s32
At this moment I use /new_net_num = 83 ! Basic + o18 + ne22 + 
alpha_mg24_to_s32/ for all runs

I'll just run a set of cases with different settings. I'm sure I'll find 
many interesting things.



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